Drying characteristics and mathematical model of CaO-conditioned oil sludge

doi:10.11949/0438-1157.20230367

Abstract

Abstract:

Thermal drying technology is one of sludge pretreatment technologies. To improve drying efficiency and reduce energy consumption, CaO was added to the oil sludge, and the microstructural changes were observed. The effects of temperature and CaO on oil sludge drying characteristics were analyzed, and the drying model of CaO-conditioned oil sludge was established. The results show that the added CaO is concentrated within the pore structure of oil sludge and increases the pore space, so moisture evaporates more easily from the pore channels. The evaporation of water is mainly concentrated in the fast drying stage, and drying at 100℃ retains the most organic matter in CaO-conditioned oil sludge. CaO shows facilitating effects on the drying process, reduces the total drying time significantly, and the optimal CaO addition ratio is 10%—12%. Page model can be used to describe the CaO-conditioned oil sludge drying process, and the effective moisture diffusion coefficient D_eff obtained by Fick's second law varies from 0.9581×10^-8 m²/s to 3.3395×10^-8 m²/s. The D_eff reaches the maximum when the CaO content is 10%. Considering the drying rate and economic benefit, the optimum drying conditions of oil sludge are at 100—120℃ and adding 10%—12% CaO.

Key words: oil sludge, drying, calcium oxide, microstructure, model

摘要：

热干化技术是一种污泥预处理技术，为提高干燥效率，降低能耗，向含油污泥中添加CaO，观察微观结构变化，分析温度和添加剂CaO对含油污泥干燥特性的影响，建立CaO调质含油污泥的干燥模型。结果表明：添加的CaO集中于含油污泥孔隙结构内，使含油污泥孔道结构增加，水分更容易从孔道中析出；水分蒸发主要集中在快干阶段，干燥温度100℃能最大限度保留CaO调质含油污泥中有机物质；添加CaO后总干燥时间显著降低，CaO最佳添加比例为10%～12%；Page模型可用于描述CaO调质含油污泥干燥过程，通过Fick第二定律得到有效水分扩散系数D_eff为0.9581×10^-8～3.3395×10^-8 m²/s，在CaO含量10%时达到最大；综合考虑含油污泥干燥速率和经济效益，干燥温度100～120℃，CaO添加量10%～12%是CaO调质含油污泥干燥的最佳条件。

关键词: 含油污泥, 干燥, 氧化钙, 显微结构, 模型

CLC Number:

X 703

Chunyu LIU, Huanyu ZHOU, Yue MA, Changtao YUE. Drying characteristics and mathematical model of CaO-conditioned oil sludge[J]. CIESC Journal, 2023, 74(7): 3018-3027.

刘春雨, 周桓宇, 马跃, 岳长涛. CaO调质含油污泥干燥特性及数学模型[J]. 化工学报, 2023, 74(7): 3018-3027.

Figures/Tables 16

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处理方法	处理规模	适应性	成本	优势	劣势
化学洗涤法	大	中	中	操作简单，处理周期短，处理量大	油品回收不彻底，产生大量含油废水
化学破乳法	大	中	中	处理速率快，使用范围广	高消耗，高污染，无法循环利用
离心法	小	中	高	技术成熟，清洁，分离效率高，占地面积小	耗能高，处理量小，设备投入高且有噪声
溶剂萃取法	中	中	高	操作简单，高效，减量化程度高，处理周期短	加热所需能耗高，大量有机溶剂污染环境
生物处理法	大	中	中	对环境适应性强，VOCs排放可控，对环境污染小	占地面积大，处理周期长
焚烧法	大	好	高	燃烧产生的热能可以二次利用，减量化程度高	需要脱水处理，需要辅助燃料，产生污染气体
干化-热解处理法	大	好	高	可以直接得到油品，处理后的污泥污染物含量低	设备复杂，消耗大量能源

处理方法	处理规模	适应性	成本	优势	劣势
化学洗涤法	大	中	中	操作简单，处理周期短，处理量大	油品回收不彻底，产生大量含油废水
化学破乳法	大	中	中	处理速率快，使用范围广	高消耗，高污染，无法循环利用
离心法	小	中	高	技术成熟，清洁，分离效率高，占地面积小	耗能高，处理量小，设备投入高且有噪声
溶剂萃取法	中	中	高	操作简单，高效，减量化程度高，处理周期短	加热所需能耗高，大量有机溶剂污染环境
生物处理法	大	中	中	对环境适应性强，VOCs排放可控，对环境污染小	占地面积大，处理周期长
焚烧法	大	好	高	燃烧产生的热能可以二次利用，减量化程度高	需要脱水处理，需要辅助燃料，产生污染气体
干化-热解处理法	大	好	高	可以直接得到油品，处理后的污泥污染物含量低	设备复杂，消耗大量能源

样品名称	工业分析（收到基）/%（质量）				元素分析（无灰基）/%（质量）					弹筒发热量（干基）/ (kJ/kg)
样品名称	水分	灰分	挥发分	固定碳	碳	氢	氮	氧	硫	弹筒发热量（干基）/ (kJ/kg)
含油污泥	49.44	19.21	23.81	7.54	62.14	7.82	0.59	27.04	2.41	18679

样品名称	工业分析（收到基）/%（质量）				元素分析（无灰基）/%（质量）					弹筒发热量（干基）/ (kJ/kg)
样品名称	水分	灰分	挥发分	固定碳	碳	氢	氮	氧	硫	弹筒发热量（干基）/ (kJ/kg)
含油污泥	49.44	19.21	23.81	7.54	62.14	7.82	0.59	27.04	2.41	18679

模型名称	模型表达式
Henderson and Pabis	MR=aexp(-kt)
Logarithmic	MR=aexp(-kt)+c
Page	MR=exp(-ktⁿ )